JPH0822135B2 - Motor rotor magnet - Google Patents

Description

TECHNICAL FIELD The present invention relates to a rotor magnet such as a rotor of a PM type step motor in which NSs are alternately magnetized in multiple poles on the circumferential surface.

[Prior art]

This type of rotor magnet has conventionally been constructed by alternately magnetizing NSs over the entire circumference of the rotor.

First, a step motor, which is a typical example of a motor using this type of rotor magnet, will be described.

The step motor is configured so that the pole teeth of a yoke having a plurality of exciting coils and the magnetic poles of the rotor are opposed to each other, and a pulse current is applied to each exciting coil in a fixed order to sequentially rotate the rotor at a fixed angle. ing.

FIG. 4 is an exploded perspective view of the step motor, and FIG. 5 is a vertical sectional view of the motor of FIG.

In FIG. 4 and FIG. 5, the step motor shown has a two-stack structure in the upper and lower directions, 11 and 12 are outer yokes of each stack, and 11a and 12a are comb-shaped magnetic poles of the outer yokes 11 and 12, respectively. , 13, 13 are the inner yokes of each stack, 13
a and 13b are comb-shaped magnetic poles of each inner yoke, 14 is a rotor shaft, and 15 is a rotor magnet in which NS is alternately poled in multiple poles.
Reference numerals 17 and 19 denote exciting coils of each stack formed by winding a coil around a bobbin.

In the motor shown in FIGS. 4 and 5, the four sets of yokes 11, 12, 13, 13 are ¼ of each other as shown in FIG.
The stator part is constructed by shifting the pitches and joining them, and the rotor magnet is coaxially arranged in the stator part.
15 are arranged facing each other.

An exciting coil 17 forming two stacks on the yoke,
19 are wound.

When the excitation phases (for example, four phases) formed by the excitation coils 17 and 19 are sequentially energized according to a predetermined sequence, the comb teeth (poles) 11a, 12a, 13a, 13b of each yoke are N or N according to the energization mode. It is magnetized by S.

The magnetized pole teeth of the yoke and the magnetic poles of the rotor magnet 15 are attracted and repelled repeatedly, and thus the rotor magnet
15 rotates and torque is obtained.

FIG. 6 shows a comb-shaped pole tooth of four pairs of yokes 11, 12, 13, and 13.
FIG. 7 is a development view showing the arrangement of 11a, 12a, 13a, 13b, and FIG. 7 shows a conventional rotor magnet.

By the way, in the conventional rotor magnet, as shown in FIG. 7, NS is alternately multipole magnetic poles over the entire surface of the rotor.

On the other hand, the comb teeth 11a, 12a, 13a, 13b of the four sets of yokes are displaced from each other by a quarter pitch as shown in FIG. 6, and face the vicinity of the central portion of the rotor magnet 15 in the axial direction. The roots of the comb teeth 13a and 13b of the yokes 13 and 13 overlap with each other as shown in FIG. 6 to form a joint bent portion (shown by the thickness C).

Originally, if the upper and lower yoke groups G1 and G2, that is, the pole teeth 11a, 13a and 12a, 13b of each stack, are magnetically separated, mutual excitation of torque by the exciting coils 17, 19 of each stack does not occur. Torque variation does not occur.

However, in the conventional rotor magnet (FIG. 7), the magnetic flux from the magnetic poles in the vicinity of the central portion in the axial direction of the rotor magnet 15 is bent at the joint bending portion (thickness C portion) of the yokes 13, 13.
Through both upper and lower yokes, causing magnetic interference between the upper and lower groups (stacks).
There is a problem that variations in the output torque of the motor and unevenness of the detent torque occur, which not only lowers efficiency but also causes vibration noise.

〔Purpose〕

The present invention has been made in view of the above prior art,
An object of the present invention is to provide a rotor magnet for a motor that can reduce or eliminate magnetic interference between the upper and lower stator parts and reduce variations in the torque of the coils of each stator part.

[Means for achieving the purpose]

According to the present invention, two stator portions each including an inner yoke and an outer yoke having a plurality of pole teeth alternately arranged in the circumferential direction and an exciting coil mounted between these yokes are provided in the inner yoke in the axial direction. In a step motor provided with a rotor magnet in which N poles and S poles are alternately arranged at a predetermined pitch in the circumferential direction on the circumferential surface in such a manner that they are coaxially arranged in these stator parts. A non-magnetized region or a magnetic pole escape portion is formed in the central portion in the axial direction, and the width of the non-magnetized region or the magnetic pole escape portion is larger than the thickness of the joint bending portion of the inner yokes of the two stator portions, and The width is set so as not to exceed the distance between the tips of the pole teeth of the yoke, and the magnetic poles on both sides of the rotor magnet whose central portion is the non-magnetized region or the magnetic pole escape portion are configured to be the same pole. The motor rotor magnet, wherein is intended to achieve the above object.

〔Example〕

The respective embodiments of the present invention shown in FIGS. 1 to 3 will be described below.
A detailed description will be given with reference to FIG. 4 or FIG.

FIG. 1 shows a first embodiment of a rotor magnet according to the present invention.

The rotor magnet 15 shown in FIG. 1 is constructed by fixing a concentric cylindrical magnet 22 to a rotor shaft 14 via a collar 21 made of a non-magnetic material such as plastic or aluminum.

The magnet 22 has an N pole and an S at a predetermined pitch in the circumferential direction.
Although the poles are magnetized alternately, a non-magnetized region 23 having a predetermined width is provided in the axial center of the magnet 22.

The width of the non-magnetized region 23 can be appropriately determined. For example, the width is larger than the thickness C of the joint bending portion of the upper and lower inner yokes 13, 13 shown in FIG. Can be significantly reduced, and can be set so as not to exceed the distance B between the tips of the comb teeth 11a and 12a of the upper and lower outer yokes.

According to the rotor magnet 15 shown in FIG. 1, since the non-magnetized region 23 having a predetermined width is provided in the central portion of the rotor 15 in the axial direction, the magnetic field between the upper and lower groups near the joint bending portion C of the yokes 13, 13 is increased. It is possible to reduce the interference, thereby reducing the variation in torque between the upper and lower exciting coils 17 and 19 (Fig. 4) and reducing the vibration noise.

FIG. 2 shows a second embodiment of the rotor magnet according to the present invention.

The rotor magnet 15 of FIG. 2 is also constructed by fixing a concentric cylindrical magnet 22 to the rotor shaft 14 via a collar 21 made of a non-magnetic material such as plastic or aluminum.

The north pole and the south pole are alternately magnetized on the circumferential surface of the magnet 22 at a predetermined pitch in the circumferential direction, which is the same as in the case of FIG. 1, but in the present embodiment, the center of the magnet 22 in the axial direction is arranged. A magnetic pole escape portion 25 having a predetermined width is formed in the portion.

The magnetic pole escape portion 25 can be formed by a groove having a predetermined depth (for example, 0.5 to 2.0 mm), and the groove may be magnetized in the same manner as the upper and lower sides thereof.

Further, the width of the magnetic pole escape portion 25 can be appropriately determined, but as in the case of the first embodiment, the comb teeth of the upper and lower outer yokes are larger than the thickness C (FIG. 6) of the joint bending portion of the yokes 13, 13. The distance can be set so as not to exceed the distance B (FIG. 6) between the tips of 11a and 12a.

The rotor magnet 15 shown in FIG. 2 has the same effect as that of the first embodiment shown in FIG.

FIG. 3 shows a third embodiment of the rotor magnet according to the present invention.

The rotor magnet 15 shown in FIG. 3 has a collar 21 made of a non-magnetic material such as plastic or aluminum having an intermediate flange 27 fixed to the rotor shaft 14, and the flange 27 on the peripheral surface of the collar 21.
Separately cylindrical (or annular) magnets 28, 28 are fixed to the upper and lower sides of the magnet.

The outer diameters of the magnets 28, 28 are substantially the same as the outer diameter of the flange 27, and the flange 27 forms a non-magnetized region, that is, a portion corresponding to the region 23 in FIG.

The rotor magnet 15 shown in FIG. 3 can also achieve the same effects as those of the first or second embodiment described above, and the torque of the upper and lower coils can be reduced by reducing the magnetic interference between the upper and lower coils. It was possible to reduce the variation of the.

The rotor magnet according to the present invention can be used as a rotor magnet for a motor having a similar structure such as a synchronous motor in addition to a step motor, and can achieve the same effect.

[Effect] As is apparent from the above description, according to the present invention, an inner yoke and an outer yoke having a plurality of pole teeth alternately arranged in the circumferential direction, and an exciting coil mounted between these yokes. Two stator portions each of which is formed by joining the inner yokes to each other in the axial direction, is coaxially arranged in the stator portions, and has N poles and S poles on the circumferential surface at a predetermined pitch in the circumferential direction.
In a step motor having a rotor magnet in which poles are arranged alternately, a non-magnetized region or a magnetic pole escape portion is formed in an axial center of the rotor magnet, and the width of the non-magnetized region or the magnetic pole escape portion is The width is set to be larger than the thickness of the joint bending portion of the inner yokes of the two stator portions and not to exceed the distance between the tips of the pole teeth of the outer yoke, and the non-magnetized region or the magnetic pole escape portion is formed in the central portion. Since the magnetic poles on both sides of the rotor magnet are configured to be the same, it is possible to reduce or eliminate magnetic interference between the two stator portions near the joint bending portion of the yoke, Provided is a rotor magnet for a motor, which can reduce variations in torque of coils in each stator section.

[Brief description of drawings]

1 is a perspective view of a first embodiment of the rotor magnet of the present invention, FIG. 2 is a perspective view of a second embodiment of the rotor magnet of the present invention, and FIG. 3 is a third view of the rotor magnet of the present invention.
FIG. 4 is an exploded perspective view of a motor suitable for using the rotor magnet according to the present invention, FIG. 5 is a vertical sectional view of the motor of FIG. 4, and FIG. 6 is FIG. 7 is a partial exploded view showing the arrangement of upper and lower yokes in the motor of FIG.
The figure is a perspective view of a conventional rotor magnet. 14 ...... Rotor shaft, 15 ...... Rotor, 22, 28 ...... Magnet, 23 ...... No magnetized area, 25 ...... Magnetic pole escape area, 27 ...... No magnetized area (colored flange).

Claims (1)

[Claims] 1. Two stator sections, each of which is composed of an inner yoke and an outer yoke having a plurality of pole teeth arranged alternately in the circumferential direction, and an exciting coil mounted between these yokes, are provided in the axial direction. A step motor having yokes joined to each other and arranged coaxially in the stators and having N poles and S poles alternately arranged on a circumferential surface at a predetermined pitch in a circumferential direction, the rotor magnet comprising: A non-magnetized region or a magnetic pole escape portion is formed in the central portion in the axial direction, and the width of the non-magnetized region or the magnetic pole escape portion is larger than the thickness of the joint bending portion of the inner yokes of the two stator portions, and The width is set so as not to exceed the distance between the tips of the pole teeth of the outer yoke, and the magnetic poles on both sides of the rotor magnet whose central portion is the non-magnetized region or the magnetic pole escape portion are configured to be the same pole. And a rotor magnet for a motor.